The present invention relates to an electronic time keeping device which displays the time of day by moving its hands by means of a stepping motor.
The electronic time keeping devices of this kind generally use a stepping motor with a small number of poles, for example, six poles or twelve poles, to make their size adequately small. They are so constructed that the rotor, stator and coil of the stepping motor are directly fixed on the ground plate and the driving force of the stepping motor shaft is transmitted to the second hand or the minute hand which is the minimum unit of time via a mechanical transfer means such as a grear-series mechanism and to the hour hand to drive it by way of another gear-series mechanism. The state of the art is such that the structure outlined above comprises many parts for mounting the pulsemotor and the gears and a complicated composition because it uses a ground plate to fasten and support the pulse motor and the gears and a pivotal receptacle plate for pivotally supporting the shafts, thereby making it necessary to aign the pivots (or bearings) on the ground plate with those on the receptacle plate when they are assembled and thus leading to high manufacturing cost and low productivity because of the onerous assembly work.
Further, the fact that the component parts such as cogwheels are tiny and thin makes the structure so delicate that it still has insufficient strength against an external shock and poor reliability. It should therefore be maintained carefully.
Accordingly, an object of the invention is to provide an electronic time keeping device which is small in size, light in weight, and low in cost, reduced in the number of parts, simplified in maintenance, and high in reliability.